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Reducing Street Sprawl Could Help Combat Climate Change by Jen Monnier in Scientific American [link]

Cities around the globe are expanding. Woodlands, farms and deserts are being paved over with roads, a transformation that is virtually irreversible—and one that can have profound consequences for global warming, depending on how sprawling the streetscapes are. Researchers have now found that city and suburban streets around the world have become less connected over the past four decades, encouraging modes of transportation that are less climate-friendly.

The new study, published last month in the Proceedings of the National Academy of Sciences USA, differed from previous papers in its approach to measuring urban sprawl. Instead of looking at how spread out residents are or how much land a city covers, the researchers created an index based on how efficiently connected streets are—in other words, how far one would have to travel to get from one point in the city to another. In a loosely connected street system filled with dead ends, roads leading to gated communities or isolated routes stretching to far-away neighborhoods, people are more likely to drive cars—a major source of greenhouse gas emissions—says study co-author Christopher Barrington-Leigh, an economist at McGill University’s School of Environment. On the opposite end of the spectrum, if streets form a tight grid, routes are shorter, walking is more convenient, and investing in public transit is more palatable to municipal governments. “The choice of the initial road layout in new development could be one of the biggest climate-relevant investments that humans are making,” Barrington-Leigh says. “And yet it’s not getting a lot of attention in policy circles.”

He and his colleagues used satellite images taken between 1975 and 2014 to document when streets started to snake through farmlands and other outlying areas around 200 cities. They analyzed the information using a measure they created called the Street-Network Disconnectedness Index, or SNDi. The more a city featured large numbers of dead ends or greater distances between intersections, for example, the more “sprawl” it was designated to have—and the higher its SNDi score was. “Their approach is quite novel,” says Richa Mahtta, a research associate studying urbanization and resource use at Yale University, who was not involved in the work.

Energy and material flows of megacities Christopher A. Kennedy et al; PNAS; 2 Apr 2015

Understanding the drivers of energy and material flows of cities is important for addressing global environmental challenges. Accessing, sharing, and managing energy and material resources is particularly critical for megacities, which face enormous social stresses because of their sheer size and complexity. Here we quantify the energy and material flows through the world’s 27 megacities with populations greater than 10 million people as of 2010. Collectively the resource flows through megacities are largely consistent with scaling laws established in the emerging science of cities. Correlations are established for electricity consumption, heating and industrial fuel use, ground transportation energy use, water consumption, waste generation, and steel production in terms of heating-degree-days, urban form, economic activity, and population growth. The results help identify megacities exhibiting high and low levels of consumption and those making efficient use of resources. The correlation between per capita electricity use and urbanized area per capita is shown to be a consequence of gross building floor area per capita, which is found to increase for lower-density cities. Many of the megacities are growing rapidly in population but are growing even faster in terms of gross domestic product (GDP) and energy use. In the decade from 2001–2011, electricity use and ground transportation fuel use in megacities grew at approximately half the rate of GDP growth.

Megacities: Environmental Friend or Foe? Mark Bessoudo

Streets with no game

Boring cityscapes increase sadness, addiction and disease-related stress. Is urban design a matter of public health?

Empty half the Earth of its humans. It's the only way to save the planet Kim Stanley Robinson; The Guardian; 20 Mar 2018

Cities are part of the system we’ve invented to keep people alive on Earth. People tend to like cities, and have been congregating in them ever since the invention of agriculture, 10,000 or so years ago. That’s why we call it civilisation. This origin story underlines how agriculture made cities possible, by providing enough food to feed a settled crowd on a regular basis. Cities can’t work without farms, nor without watersheds that provide their water. So as central as cities are to modern civilisation, they are only one aspect of a system.
There are nearly eight billion humans alive on the planet now, and that’s a big number: more than twice as many as were alive 50 years ago. It’s an accidental experiment with enormous stakes, as it isn’t clear that the Earth’s biosphere can supply that many people’s needs – or absorb that many wastes and poisons – on a renewable and sustainable basis over the long haul. We’ll only find out by trying it.
Right now we are not succeeding. The Global Footprint Network estimates that we use up our annual supply of renewable resources by August every year, after which we are cutting into non-renewable supplies – in effect stealing from future generations. Eating the seed corn, they used to call it. At the same time we’re pumping carbon dioxide into the atmosphere at a rate that is changing the climate in dangerous ways and will certainly damage agriculture.
This situation can’t endure for long – years, perhaps, but not decades. The future is radically unknowable: it could hold anything from an age of peaceful prosperity to a horrific mass-extinction event. The sheer breadth of possibility is disorienting and even stunning. But one thing can be said for sure: what can’t happen won’t happen. Since the current situation is unsustainable, things are certain to change.
Cities emerge from the confusion of possibilities as beacons of hope. By definition they house a lot of people on small patches of land, which makes them hugely better than suburbia. In ecological terms, suburbs are disastrous, while cities can perhaps work.
The tendency of people to move to cities, either out of desire or perceived necessity, creates a great opportunity. If we managed urbanisation properly, we could nearly remove ourselves from a considerable percentage of the the planet’s surface. That would be good for many of the threatened species we share this planet with, which in turn would be good for us, because we are completely enmeshed in Earth’s web of life.
Here I’m referring to the plan EO Wilson has named Half Earth. His book of the same title is provocative in all the best ways, and I think it has been under-discussed because the central idea seems so extreme. But since people are leaving the land anyway and streaming into cities, the Half Earth concept can help us to orient that process, and dodge the sixth great mass extinction event that we are now starting, and which will hammer humans too.
The idea is right there in the name: leave about half the Earth’s surface mostly free of humans, so wild plants and animals can live there unimpeded as they did for so long before humans arrived. Same with the oceans, by the way; about a third of our food comes from the sea, so the seas have to be healthy too.
At a time when there are far more people alive than ever before, this plan might sound strange, even impossible. But it isn’t. With people already leaving countrysides all over the world to move to the cities, big regions are emptier of humans than they were a century ago, and getting emptier still. Many villages now have populations of under a thousand, and continue to shrink as most of the young people leave. If these places were redefined (and repriced) as becoming usefully empty, there would be caretaker work for some, gamekeeper work for others, and the rest could go to the cities and get into the main swing of things.
So emptying half the Earth of its humans wouldn’t have to be imposed: it’s happening anyway. It would be more a matter of managing how we made the move, and what kind of arrangement we left behind. One important factor here would be to avoid extremes and absolutes of definition and practice, and any sense of idealistic purity. We are mongrel creatures on a mongrel planet, and we have to be flexible to survive. So these emptied landscapes should not be called wilderness. Wilderness is a good idea in certain contexts, but these emptied lands would be working landscapes, commons perhaps, where pasturage and agriculture might still have a place. All those people in cities still need to eat, and food production requires land. Even if we start growing food in vats, the feedstocks for those vats will come from the land. These mostly depopulated landscapes would be given over to new kinds of agriculture and pasturage, kinds that include habitat corridors where our fellow creatures can get around without being stopped by fences or killed by trains.
This vision is one possible format for our survival on this planet. They will have to be green cities, sure. We will have to have decarbonised transport and energy production, white roofs, gardens in every empty lot, full-capture recycling, and all the rest of the technologies of sustainability we are already developing. That includes technologies we call law and justice – the system software, so to speak. Yes, justice: robust women’s rights stabilise families and population. Income adequacy and progressive taxation keep the poorest and richest from damaging the biosphere in the ways that extreme poverty or wealth do. Peace, justice, equality and the rule of law are all necessary survival strategies.


Superblocks: how Barcelona is taking city streets back from cars David Roberts; Vox; 4 Aug 2016

once you’ve got a city that’s mostly composed of street grids, devoted to moving cars around, how do you take it back? How can cities be reclaimed for people?


sky city

A Chinese entrepreneur who took just 19 days to build a 57-storey tower says he has triggered a construction revolution. And his dreams soar far, far higher.

Green cities

Hanging highway garden in São Paulo would filter 20% of car emissions Nicole Jewell; inhabit; 30 May 2016

Franco-Brazilian firm Triptyque Architecture has unveiled an ambitious plan to convert the long-neglected Minhocão viaduct undersection into a vibrant public space covered in suspended plants. Working with landscape architect Guil Blanche, the architects plan to hang oxygen-heavy plants over three kilometers of the elevated section to filter 20 percent of CO2 emissions.

Why rooftop gardens cool cities Jan Ellen Spiegel; Yale Climate Connections; 19 Mar 2018

City rooftops are getting a makeover. Instead of concrete, many are now covered by grasses, flowers, and even small trees.
Andy Creath, president of Green Roofs of Colorado, says green roofs are not just pretty. They benefit the climate too.
Creath: “Green roofs actually cool cities.”
By replacing heat-absorbing materials like concrete and tar, green roofs help to lower the temperature of the air around them. And, they act as insulators for buildings, which reduces the energy needed for heating and cooling.
Plus, green roofs absorb water, which helps reduce storm run-off. They can create habitat for birds and pollinators. And in some places, they’re even used to grow vegetables.

Inside the breathtaking urban jungle that could be coming to Europe Jack Williams; Mirror; 22 Mar 2018

Vincent Callebaut's plans for the City of Angers, France, feature a series of blooming green balconies that make for a beautiful spectacle, the natural exterior fusing into shops, restaurants and apartments, public spaces, bars and a concert hall.
The dynamic development, Vincent said, was inspired by childhood dreams of building tree houses and interacting with nature.
This plan was part of the "Imagine Angers" competition, which called for proposals to transform the city.
In order to develop his designs, Vincent collaborated with a landscaping firm and a real estate developer.
In total, the plot would fill some 9,400 square meters in a city that has been dubbed the Europe's "Plant Capital."
Vincent named the project "Arboricole" - from the Latin words "arbor" (tree) and "colo" (cultivate) - and he admits that the designs were targeted at those aged between 25 and 35.